– Fertilization under normal conditions: 1 chance out of 4
– Fertility period: depending on the age of the woman
– 1st design at 30: evolution of society
– Recourse to LDCs and the decline in the age of the first childbearing
In the USA, the average age of first procreation is 26.3 (source: The New York Times, The Age That Women Have Babies: How a Gap Divides America). The fertilization of an ovum requires the woman to be fertile, which a fertility test can better identify.
Fertilization under normal conditions: 1 chance out of 4
The fertile period of a woman’s menstrual cycle depends on two factors:
– the ability of the oocyte (egg) to wait for the sperm for approximately 24 hours,
– the duration of the sperm in the female genital tract.
These variables explain the fact that there is only a one in four chance of achieving fertilization.
During the fertile period of a woman’s life (from 18 to 30 years), a statistical calculation puts the capacity to be fertilized at around 25%: there is statistically one chance in four cycles that a gestation (pregnancy) will occur.
These limits explain the false infertilities that give way after a few months of waiting.
Note: this recent observation has prompted practitioners to propose a waiting period of a few months, or even a year, before treating couples for infertility.
Fertility period: depending on the age of the woman
The fertility curve in women is optimal between the ages of 18 and 30.
Fertility: no more waiting after the age of 30.
This curve then descends :
– first slowly, after 30 years,
– then, the oocyte stock inevitably runs out.
This biological fact explains why, after the age of 30, it is necessary to wait for fertilization to occur. After the age of 35 :
– Fertilization becomes random and may require several months or even years of waiting,
– the biological processes of fertilization become less efficient.
Relative infertility: lengthening of the waiting period
In developed countries, the first pregnancy age is inexorably decreasing: 26 years on average in the USA (as seen above). This delay in conception is in itself :
– a cause of relative infertility in couples, i.e., a lengthening of the waiting period for natural fertilization,
– the reason for many consultations of couples for infertility.
1st conception at age 26: evolution of society
In industrialized and developed countries, a growing number of patients are complaining of infertility that biology can only explain imperfectly. Delayed first conception (pregnancy) is increasingly the cause.
There are 3 main reasons for this:
– the sociological context has changed: for the last 50 or 60 years, the increase in life expectancy, the preservation of a youthful appearance, and the lengthening of the duration of studies have pushed back conception even further,
– the comfort of contraception (birth control) pushes the age of first pregnancy back to 30 years on average in other developed countries like France,
– educational and professional achievement is later, making it difficult for women to combine work and family life.
Recourse to MAP and delaying the age of the first childbearing
In developed and industrialized countries, the delay in the first pregnancy age makes it more difficult for some couples to procreate. Some women remain fertile and do not wait until the age of 30 to become pregnant. However, others will have to wait months or even years and consult for infertility. This delay at first conception is leading to increased recourse to Medically Assisted Procreation (MAP).
Ending this post on a positive note, hopefully, MAP is a successful way to conceive a baby. According to the U.S. 2003 CDC (Centers for Disease Prevention) report on Assisted Reproductive Technology (ART), the average percentage of ART cycles that led to a healthy baby was 37.3% in women under 35 and 30.2% in women aged 35-37.